Not applicable.
Not applicable.
The keeping of matter in sealed containers is widely practiced. As a well-known and very prevalent example, food is kept in sealed bags, both commercially and by members of the public, to preserve its freshness and to protect from contamination. The production of sealable plastic bags is carried on by several large companies, and there have been many U.S. patents granted for sealing closure strips, for example, U.S. Pat. Nos. 3,416,199, 4,186,786, 4,212,337, 4,285,105, 4,362,198, 4,363,345, 4,578,813, 4,791,710, 4,829,641, 4,863,286, 4,878,763, 5,007,143, 5,010,627, 5,017,021, 6,033,113, and 6,185,813. The author of the present invention holds U.S. Pat. No. 5,142,970 relating to the extraction of gas from conventionally sealed bags, in order to achieve what is commonly known as xe2x80x9cvacuum packingxe2x80x9d, which means in most, if not all, cases partial vacuum packing. In vacuum packing a pressure difference is created between the higher pressure outside the bag and the lower pressure inside the bag, but a pressure difference in the opposite direction may occur if the bag is overloaded or shaken to release trapped or dissolved gas as in the case of soda water, for example, or if the bag is used in applications in outer space, as another example. The seals for flexible plastic bags available hitherto have consisted of two strips, one along each side of the bag opening, capable of being squeezed together either manually or by an slider operating over both strips along their lengths. One of the strips has an undercut groove or series of grooves into which snaps, when the strips are pressed together, a corresponding male element or series of such elements molded onto the other strip, to give a notional seal along the now closed bag access end. For instance, in conventional bag seals, the first strip may have a groove undercut, molded or extruded with the cross-sectional profile of a mushroom-shaped space, while the other strip has a protrusion of a similarly-shaped profile. The weakness of this conventional design is that in order to enable the sealing strips to be capable of being snapped together, there must be a tiny clearance space between the female and male strip elements, which means that the notional seal formed thereby is never entirely leak-proof. In addition, because these conventional strips are squeezed together in respective directions at right angles to the bag walls in order to effect the notional seal, they tend to be separated by an excess of pressure inside the bag over the pressure outside the bag, again tending to cause leakage. The conventional xe2x80x9csealingxe2x80x9d strips available hitherto could more accurately be termed xe2x80x9cclosurexe2x80x9d strips, because their sealing abilities are nominal at best. In the course of research by the present inventor it was discovered that none of the press or slide sealing closure strips available at prices economical for the retail public, were satisfactorily fluid-tight, the word xe2x80x9cfluidxe2x80x9d being used throughout herein in its usual meaning of liquid or gas or a mixture of both, and, in addition, powder. Pressure differences in either direction across the available sealing strips tended to force them apart and promote leakage, so that the only remedy for adequately vacuum-packed substances such as food intended to be stored for extended periods was in heat-sealing the bags. Heat-sealing of course involves melting the opposing sides of the bag together, so that the bag must be cut open to access its contents. The desirable feature of being able to reseal, and exhaust residual air from, the bag after extracting part of the contents was therefore not available on the consumer-oriented market, and it is one of the subsidiary benefits of the present invention that vacuum packed bags can be partially unloaded and then safely re-used. It was the necessity of obtaining a cheap fluid-tight seal for further developments in adequate vacuum packing that led to the present invention, which is a slide-operated sealing strip combination capable of low-cost production and so designed as to provide a sealing effect that increases the greater the pressure difference across it, that is, the reverse of the undesired leakage tendency that is evident in the strip seals available hitherto. Instead of the space between the conventional sealing elements, the present invention features extensive sealing surfaces that press more tightly together as the pressure differential in either direction increases, and the sealing effect, instead of being at right-angles to the bag walls as in the conventional seals available hitherto, is in the plane of internal contact of the sheets of the bag when empty and hanging vertically from the sealing strips, that is, at right angles to the direction of conventional seals. This increased sealing effect characteristic of the present invention effectively renders this invention the only reusable sealing device possible for use with vacuum packing in flexible bags.
A slide-operated sealing strip combination was disclosed in the present inventor""s provisional Patent Application No. 60/322,059 filed on Sep. 14, 2001. That disclosure was supplemented by the present inventor""s filing on Dec. 27, 2001 of Disclosure Document No. 502505.
This invention is a flexible container seal which may be opened and closed by the operation of a slider on two sealing strips of complementary profiles, and provides a sealing effect which tends to become more resistant to leakage the greater the pressure difference is across the seal. The invention is particularly applicable to the fluid-tight sealing of conventional flexible plastic bags that are commonly made of two rectangular flexible plastic sheets of the same size joined together by heat or other means along three corresponding sides, leaving the fourth side open to provide access to the bag interior. The edges of the fourth side lie together when the bag is empty. Alternatively, to form a bag, a single rectangular plastic sheet may be folded in half and two of the remaining sides are then joined together, also leaving an open side of the same form.
This invention comprises two complementary sealing strips, attached by conventional means to, or molded with, the edges of the bag opening, one sealing strip along each of the two edges, which in bags in common use are conventionally straight, of the bag opening. The bag opening edges may be curved, and in that case the sealing strips are likewise curved, but that case, in the absence of special uses requiring such configuration, would be rare. The sealing strips have transverse cross-sectional profiles which are essentially in thickened short-shank hook form, one having a male ridge with a curved profile along its length, and the other having a female channel to fit the male ridge.
The ridge and channel are so positioned on the respective hook-shaped profiles of the sealing strips that the male ridge snap-fits into the female channel when the sealing strips reach their closed position, in order to hold the sealing strips in that closed position. The presence of the ridge and channel leads to their respective sealing strips being termed male and female herein.
However, in this invention, when the bag is open and in an upright position, the male and female profiles are not, contrary to the conventional design, so disposed that they can be pushed together horizontally, that is, in respective directions at right-angles to the bag walls, to form an interlocking seal. In conventional bag seals the sealing strips are pushed together horizontally, either manually or by operation of a slider, in order to form a seal which has a tendency not to be leak-proof, because a pressure difference in either direction across the interlocking portions of strips will tend to pull or push them apart, and there is a clearance space left between the two horizontally interlocking elements to enable the interlocking to take place. In the present invention, by contrast, the male and female profiles, again when the bag is considered to be in a vertical position, are so shaped and disposed in the strips that they must be moved in a vertical direction towards each other before interlocking can take place between them. In certain embodiments of this invention there must take place for the purpose of interlocking both vertical and horizontal movement, and in certain other embodiments a rotational movement also. The reason for this novel vertical movement of the novel strip profiles of this invention will be apparent from the drawings and Detailed Description herein, but the result is that interlocking along the lengths of the sealing strips, that is, along the bag opening, would be difficult to achieve manually. For that reason, a slider of an inverted U-type shape is provided in this invention, straddling the top and side exterior surfaces of the sealing strips and so arranged as to be slid manually along them. The interior of the slider is so arranged in each embodiment of this invention that the slider, as it is slid along the strips in the bag-open to the bag-closed position, guides the strips into the necessary vertical and other movements described as necessary for interlocking the strip profiles in a vertical fluid-tight position, with the bag closed. As will be seen in the drawings of the present invention, the crosssectional profiles of the novel sealing strips are so arranged that when in their interlocked positions absolute contact is maintained, without surface penetration which would require clearance spaces to fit, between extensive surfaces of the strips, precluding leakage tendencies. Sliding the slider in the reverse position reverses the profile movements and opens the strip and the attached bag. The vertical disposition of the interlocked strip profiles, that is, when the bag is closed, means that a difference in pressure between the interior and the exterior of the bag will press the profiles together, tending to form a more leak-proof seal, contrary to the conventional, horizontal seals available hitherto.